Bond pad structure with dual passivation layers

ABSTRACT

A bond pad structure with dual passivation layers is disclosed. The bond pad structure includes: a pad material layer on a first passivation layer; a protection layer on the top surface of the pad material layer; a second passivation layer covering on the first passivation layer and the protection layer; and an opening formed through the second passivation layer and the protection layer to expose the pad material layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 13/659,924filed Oct. 25, 2012, and incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a bond pad structure and,more particularly, to a bond pad structure with a protection layer.

2. Description of the Prior Art

In semiconductor manufacturing, a fabricated integrated circuit (IC)device is typically assembled into a package to be utilized on a printedcircuit board (such as a motherboard, etc) as part of a larger circuit.When the fabrication of the integrated circuit device (such as a die) isfinished, the integrated circuit device is immovably bound and sealedusing an electronic package technique so as to prevent damages from anexternal force or other environmental factors. A package substrate isoften used in the electronic package industry to affix the integratedcircuit device thereon, and it also provides one or more layers of metalinterconnects, wherein one end of the metal interconnect is electricallyconnected to the integrated circuit device, and the other end thereof iselectrically connected to the other electronic modules. The metal bondpad (or referred to as bonding pad) is designed to be in the openings ofthe passivation layer (i.e. topmost insulating layer) of the integratedcircuit device as a mean to connect the metal interconnects of thepackage substrate to the integrated circuit device.

In the past, aluminum or aluminum alloys, such as AlCu alloy or AlSiCualloy, have been used as conventional chip wiring materials. Morerecently, aluminum wiring material has been replaced by copper andcopper alloys with damascene process, since copper wiring can providesimproved chip performances and superior reliability when compared toaluminum and aluminum alloys. However, in the packaging of IC devices,employing copper wiring may induce a number of process issues, such asthe reaction of copper with the material used in the ball-solderingprocess, and/or the susceptibility of copper to the environmentaldamages and corrosion. To solve these process issues, a terminalaluminum pad or aluminum cap structure is designed to be formed on thecopper interconnection for protecting the copper from environmentaldeterioration.

Although the use of an aluminum pad/cap structure on the copperinterconnection may solve the conventional copper deterioration issues,it still has some process drawbacks to improve. As well-known in thesemiconductor field, aluminum materials are quite vulnerable to thecorrosion issue, especially for the aluminum structure in theaforementioned pad loop. In this process stage, a thick photoresistlayer used for patterning the aluminum pad may leave residues on thesurface of aluminum layer due to the PR hardening, thereby significantlyincreasing the possibility of Al corrosion. This is major cause of theso-called “pad discoloration” issue.

Therefore, while aforementioned existing methods of fabricating bond padstructures for semiconductor devices have been generally adequate fortheir intended purposes, they have not been entirely satisfactory inevery aspect . There is still a need to improve the bond pad structureand the manufacturing method thereof in order to provide larger processwindows as well as to lower the process costs.

SUMMARY OF THE INVENTION

To improve the above-mentioned drawbacks in the fabrication of the bondpad in prior art, a novel method of manufacturing a bond pad structureis provided in the present invention. A protection layer is used inpresent invention to cover the pad material layer before the padmaterial layer is etched and patterned into a bond pad. The protectionlayer is suitable for protecting the underlying pad material layer fromcorrosion or pad discoloration issue, thereby providing a larger processwindow for the bond pad loop. Moreover, the protection layer may beeasily removed from the underlying bond pad structure by a simple stripor wet etching process after forming the bond pad, so this approach maylower the possibility of bond pad damage during the etching process andlower the manufacturing costs.

One object of the present invention is to provide a method ofmanufacturing a bond pad structure comprising the steps of forming a padmaterial layer on a passivation layer, forming a protection layer on thepad material layer, using a photoresist as a mask to perform an etchingprocess for patterning the protection layer and the pad material layerinto a bond pad structure, and removing the protection layer on the bondpad structure.

Another object of the present invention is to provide a method ofmanufacturing a bond pad structure comprising the steps of forming a padmaterial layer on a first passivation layer, forming a protection layeron the pad material layer, performing a first etching process to patternthe protection layer and the pad material layer into a bond padstructure, forming a second passivation layer on the bond pad structureand the first passivation layer, and performing a second etching processto remove a part of the second passivation layer and the protectionlayer so that the bond pad structure is exposed.

According to another aspect of the present invention, a bond padstructure with dual passivation layers is disclosed. The bond padstructure includes: a pad material layer on a first passivation layer; aprotection layer on the top surface of the pad material layer; a secondpassivation layer covering on the first passivation layer and theprotection layer; and an opening formed through the second passivationlayer and the protection layer to expose the pad material layer.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the embodiments, and are incorporated in and constituteapart of this specification. The drawings illustrate some of theembodiments and, together with the description, serve to explain theirprinciples.

In the drawings:

FIGS. 1-6 are cross-sectional views illustrating the process flow ofmanufacturing a bond pad structure with single passivation in accordancewith the first embodiment of the present invention; and

FIGS. 7-10 are cross-sectional views illustrating the process flow ofmanufacturing a bond pad structure with dual passivations in accordancewith the second embodiment of the present invention.

It should be noted that all the figures are diagrammatic. Relativedimensions and proportions of parts of the drawings have been shownexaggerated or reduced in size, for the sake of clarity and conveniencein the drawings. The same reference signs are generally used to refer tocorresponding or similar features in modified and different embodiments.

DETAILED DESCRIPTION

In following detailed description of the present invention, reference ismade to the accompanying drawings which form a part hereof, and in whichis shown, by way of illustration, specific embodiments in which theinvention may be practiced. These embodiments are described insufficient details to enable those skilled in the art to practice theinvention. Other embodiments may be utilized and structural, logical,and electrical changes may be made without departing from the scope ofthe present invention.

The embodiments will now be explained with reference to the accompanyingdrawings to provide a better understanding of the process of the presentinvention, wherein FIGS. 1-6 are cross-sectional views illustrating theprocess flow of manufacturing a bond pad with a single passivationconfiguration in accordance with the first embodiment of presentinvention; and FIGS. 7-10 are cross-sectional views illustrating theprocess flow of manufacturing a bond pad with dual passivationsconfiguration in accordance with the second embodiment of presentinvention.

Please now refer to FIGS. 1-6, which illustrates the process flow infirst embodiment of the present invention. The process of the presentembodiment is particularly directed to form a protruding bond padstructure which is suitable for direct wire bonding in packagingprocesses.

First, the process of present embodiment starts from a prepared copperinterconnection, for example: a top metal Cu layer or a Cu contact. Asshown in FIG. 1, this copper structure may be a copper layer 101deposited within a patterned opening formed in an insulating layer 103,such as a layer made of fluorinated TEOS (tetraethoxysilane) orfluorinated silicate glass (FSG). In the first place, the copper layer101 is designed to serve as a contact for connecting the externalelectrical circuit. However, as mentioned in the description of theprior art, a copper interconnection may usually require an aluminum capor pad structure to protect the copper from environmental deterioration,such as oxidation from the ambient atmosphere. To form this aluminum padstructure, a passivation layer 105 is first deposited on the preparedcopper layer 101 and the insulating layer 103. In the presentembodiment, the passivation layer 105 may be a multilayer structure oran insulating stack made of successive silicon nitride layer (SiN) 106,silicon oxide layer (such as plasma enhanced silicon oxide layer) 107,and a silicon nitride layer (SiN) 108. The passivation layer 105 mayprovide protection to the underlying copper layer 101, and also providespace to form a via or an opening for receiving the aluminum padstructure. As shown in FIG. 1, an opening or a via 110 is formed throughthe entire passivation layer 105 to expose a part of the underlyingcopper layer 101. This may ensure that the ensuing aluminum pad formedin later process may have a good electrical connection with the copperlayer 101.

Before forming the ensuing aluminum pad structure, it is preferable inthe process to form a barrier layer 109 on the copper layer 101 to serveas a diffusion barrier between the copper layer 101 and the ensuingaluminum pad. As shown in FIG. 2, the barrier layer 109 is conformallyformed over the copper layer 101 and the passivation layer 105,including the sidewalls of opening 110. The material of the barrierlayer 109 may be Ti, TiN, Ta, TaN, TiW, WN or a combination thereof,which may efficiently prevent the inter-migration of Cu atoms and Alatoms in the copper layer 101 and the ensuing aluminum pad (referredhereafter as Al pad) once the copper layer 101 is in contact with the Alpad.

After the barrier layer 109 is formed, please refer again to FIG. 2, apad material layer 111 (ex. an aluminum layer) is deposited throughphysical vapor deposition or chemical vapor deposition over the barrierlayer 109. The material of the pad material layer 111 may be aluminum oran aluminum alloy made of AlCu or AlSiCu. A portion of the pad materiallayer 111 fills up the opening 110 to form a plug-like structure whichis connected to the exposed copper layer 101. The deposited pad materiallayer 111 will be patterned into pad shape in following process.

Before patterning the pad material layer 111 into bond pads, pleaserefer to FIG. 3, a protection layer 113 is first deposited on the padmaterial layer 111. In this embodiment of the present invention, theprotection layer 113 is designed to grant the conventional bond padprocess loop larger process window. The material of the protection layer113 may be selected from the group of dielectric materials, such asundoped silicon carbide (SiC) , doped silicon carbide (ex. SiC (N,H,O)), silicon oxynitride (SiON), oxide and nitride, or the group of inertmetal, such as Ti or TiN, wherein the non-metal dielectric material ispreferred in order to grant the protection layer 113 different etchingselectivity from the metal pad material layer 111 (ex. Al or AlCu) inthe following patterning processes, and also to make the protectionlayer 113 easy to be removed.

After the protection layer 113 is deposited on the pad material layer111, please refer to FIG. 4, a patterned photoresist 115 is formed onthe protection layer 113 by photolithographic process. The photoresist115 is used to define the position and shape of the desired aluminum padon the passivation layer 105. Preferably, the photoresist 115 will bealigned with the underlying copper layer 101, with a coverage arealarger than the opening 110. Alternatively, in some embodiment ofpresent invention, a bottom anti-reflective coating (BARC) 114 may beprovided between the photoresist 115 and the protection layer 113 toreduce the light reflection at the interface between the photoresist 115and the dielectric protection layer 113.

Please refer now to FIG. 5, an etching process is then performed withthe photoresist 115 as an etching mask to shape an aluminum pad. Theetching process will remove parts of the dielectric protection layer113, the pad material layer 111, the barrier layer 109, or even parts ofthe SiN layer 108. Through this etching process, a protruding Al bondpad 116 is shaped on the passivation layer 105, which is electricallyconnected to the underlying copper layer 101. Thereafter, the residuephotoresist 115 and BARC 114 on the bond pad 116 is removed by regularstrip process.

After the bond pad 116 is formed, please refer to FIG. 6, the protectionlayer 113 should also be removed prior to the wire bonding process inorder to expose the pad material layer 111. In this embodiment of thepresent invention, the removal of protection layer 113 may be easilyachieved by a simple Al etch strip, a wet etching, or a post-etch cleantreatment, without any extra steps or cost. This advantage may becredited to the material used in the dielectric protection layer 113,which was selected from the material which can be easily removed andhave a different etching rate from the underlying pad material layer(ex. Al layer) 111.

In addition to the easy removing process, another advantage of presentinvention is: with the protection of inert protection layer 113, theunderlying Al layer will be free from the corrosion problem resultingfrom the PR residue or PR hardening on the Al layer after the PR stripprocess. Moreover, the easy removal of the protection layer 113 may alsocompletely remove the PR or BARC residue from the bond pad 116. This mayfurther lower the occurrence of Al corrosion or pad discoloration issue.

In the present embodiment, optionally, the completed bond pad 116 may befurther covered with a topmost passivating polyimide layer (not shown)before the wire bonding or probe test step, depending on the process orproduct requirement.

Now, please refer to FIGS. 7-10 which illustrate the cross-sectionalview of a process flow for manufacturing a bond pad structure with dualpassivations in accordance with the second embodiment of presentinvention.

The process of the present embodiment is particularly directed to forman embedded bond pad structure wherein each Al bond pad is embedded in,rather than protruding from the passivation layer. This kind of embeddedbond may be suitable for processes or packaging with solder balllimiting metallurgy (BLM) or solder bumps.

As shown in FIG. 7, the present embodiment starts from a prepared padstructure similar to the bond pad 116 shown in FIG. 5, wherein theprotection layer 113 is still present on the bond pad structure, and thephotoresist 115 and BARC 114 used in pad etching process have alreadybeen removed. The difference between the bond pad structures shown inFIG. 5 and FIG. 7 is that the passivation layer 105 of the bond padstructure in FIG. 7 is made of only a SiN layer 106 and a PEOX layer107.

In order to form a pad structure suitable for the ball bonding, pleaserefer to FIG. 8, another passivation layer (i.e. second passivationlayer) 117 is necessary to cover the prepared Al bond pad 116. Thepassivation layer 117 can provide space to form a predetermined openingor a via for ball limiting metallurgy or for the placement of the solderball. In this embodiment, the passivation layer 117 may be a multilayerstructure or an insulating stack made of a FSG layer 118 and a SiN layer119. The passivation layer 117 may combine with the underlyingpassivation layer (i.e. the first passivation layer) 105 and encompassthe entire bond pad 116.

After the passivation layer 117 is deposited on the bond pad 116, pleaserefer to FIG. 9, a patterned photoresist 121 is formed on thepassivation layer 117 by photolithographic process. Unlike the firstembodiment, the photoresist 121 is designed to define an opening or avia in the passivation layer 117 for exposing the underlying bond pad,rather than to define the bond pad. Preferably, the opening defined bythe photoresist 115 is aligned with the opening 110 and is smaller thanthe area of the underlying bond pad 116.

Subsequently, please refer to FIG. 10, an etching process is performedby using the photoresist 121 as a mask. The etching process may beanisotropic dry etching process which removes a part of the FSG layer118, of the SiN layer 119 and of the protection layer 113, therebyforming an opening or a via 123 which exposes the pad material layer 111(ex. a conductive Al layer) for the embedded bond pad 116 toelectrically connect with external interconnection structures, such as aunder-ball-metallurgy (UBM) layer, a solder ball or a solder bump.

The protection layer 113 in this embodiment of present invention may beeasily removed along with the overlying passivation layer 117 by singledry etching process, without damaging the underlying bond pad structure.This is due to the materials of the dielectric protection layer 113 andoverlying passivation layer 117 are preferably non-metal materials andmay have a good etching selectivity to the underlying metal pad materiallayer 111. Accordingly, the design of protection layer 113 on the bondpad structure not only can reduce the process costs and steps tomanufacture an embedded bond pad, but can also improve the processwindow of the involved etching processes.

According to the second embodiment of present invention, a bond padstructure with dual passivations is provided, comprising a bond pad 116formed on a first passivation layer 115, a protection layer 113 formedon the top surface of said bond pad, a second passivation layer 117covering on the first passivation layer 115 and the protection layer113, and an opening 123 formed through the second passivation layer 117and the protection layer 113 to expose the bond pad 116.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A bond pad structure with dual passivationlayers, comprising: a pad material layer on a first passivation layer; aprotection layer on the top surface of the pad material layer; a secondpassivation layer covering on the first passivation layer and theprotection layer; and an opening formed through the second passivationlayer and the protection layer to expose the pad material layer.
 2. Thebond pad structure with dual passivation layers according to claim 1,wherein the pad material layer comprises aluminum or aluminum alloy. 3.The bond pad structure with dual passivation layers according to claim2, wherein the aluminum alloy comprises AlCu or AlSiCu.
 4. The bond padstructure with dual passivation layers according to claim 1, furthercomprising a barrier layer between the first passivation layer and thepad material layer.
 5. The bond pad structure with dual passivationlayers according to claim 4, wherein the barrier layer comprises Ti,TiN, Ta, TaN, TiW, WN, or combination thereof.
 6. The bond pad structurewith dual passivation layers according to claim 4, wherein an edge ofthe protection layer is aligned with an edge of the barrier layer. 7.The bond pad structure with dual passivation layers according to claim1, wherein an edge of the protection layer is aligned with an edge ofthe pad material layer.
 8. The bond pad structure with dual passivationlayers according to claim 1, wherein an edge of the protection layer isaligned with an edge of the opening.
 9. The bond pad structure with dualpassivation layers according to claim 1, wherein the protection layer isselected from the group of dielectric undoped SiC, doped SiC, SiON,oxide or nitride, or inert Ti or TiN.
 10. The bond pad structure withdual passivation layers according to claim 1, wherein the firstpassivation layer comprises a first SiN layer, a PEOX layer, and asecond SiN layer.
 11. The bond pad structure with dual passivationlayers according to claim 1, wherein the first passivation layercomprises a SiN layer and a PEOX layer.
 12. The bond pad structure withdual passivation layers according to claim 1, wherein the secondpassivation layer comprises a FSG layer and a SiN layer.
 13. The bondpad structure with dual passivation layers according to claim 12,wherein an edge of the FSG layer is aligned with an edge of theprotection layer.
 14. The bond pad structure with dual passivationlayers according to claim 12, wherein an edge of the SiN layer isaligned with an edge of the protection layer.